Gear pump



Dec. 28, 1943. G. A. UNGAR GEAR PUMP Filed June 13, 1940 4 Sheets-Sheet l INVENTOR GUSTAVE A. UNGAR V (9 ATTORNEY G. A. UNGAR I GEAR PUMP Dec. 28; 1943.

F iled June 13,

4 Sheets-Sheet 2 emu um vmn INVENTOR GUSTAVE A. UNGAR Y ATTORNEYS Dec. 28, 1943.

G, A. UNGAR ,GE'AR PUMP 4 Sheets-Sheet 4 Filed Jilne 15, 1940 Fig. l9

Fig. l7

NTOR x 4 A. UNGAR thrust on the gears.

Patented Dec. 28,1943

UNITED STATES PATENTFOFFIVCET GEAR PUMP Gustave A. Ungar, Pelham Manor, N. Y., assignor to Joseph F. Keller, New York, N. Y.

Application June 13, 1540, Serial No. 340,239

20 Claims. 401. 103-128) This invention relates to gear pump p cially helical gear pumps .using single helical gears, and to an arrangement for hydraulica axially balancing the same.

To avoid noise in gear pumps, it is desirable to use helical gears rather than spurgears. For

' size pumps. If single helical gears. are employed,

difliculty arises because of axial thrust, one

gear trying to move axially in one direction,

and'the other trying to move axially inthe-othcr a direction.

end face to hydraulic pressure and so aggravating the unbalance and increasing gear wear.

The primary object of the present invention is to overcome this difliculty by hydraulically balancing the gear thrust.. A -corollam ,object is,

to provide a counterbalancing force which is proportional to the delivery pressure of the pump. For this purpose, I provide axial balance pressure ports in the pump casing at that side of the g ear Which tends to move toward the casing. I may further provide axial balance suction ports in the casing at that'side of the gear which tends to move away from the casing. Of course,

Unless specialthiiisfi"bearingsare employed, the clearance is eliminated on oneside, and exaggerated on the other, exposing the of the gears, the radial balance pressure ports being located diametrically opposite the pump-. ing pressure port, and the radial balance suction ports being. located diametrically opposite the pumping suction port. Inaccordance with a further feature and object of the present invention, the axial balance ports are combined with the radial balance ports, one being, in effect, a

direct continuation or extension' of the other. For the sake of symmetry, and to avoid any tilting or wobble force on the gears, axial balance ports are located diametrically'opposite one another, the inner ones being formed directly in communication with the main pumping ports.

The other balance portsarecomTected to the appropriate' pumpingiibrts by suitable passages which mayrun to either the axial or radial balance ports, whichever may be more. convenient, for these are in direct communication another. I

, To the accomplishment of' the foregoing main objects and other more specific objects which will hereinafter appear, my invention consists ,:Q the single helical gear pump elements and their reEtion one'fd the otherashereinafter are more particularly described in the specification.

- and sought to be defined in the claims. The

the position of the ports for'the two gears is reversed, the pressure ports of one gear being on the same side of the casing as the suction ports of the other gear.

The area of the ports determines the counterbalancing force at any given pressure. It may be pointed out that the torque and'consequently the tooth pressure is proportional to the hydraulic pressure, and that inasmuch as the axial force is proportional to the tangential force or tooth pressure, it follows that the axial gear thrust remains substantially proportional to the hydraulic pressure. However, for a given port area, 'the counterbalancing force is also proportional to the hydraulic pressure. Consequently, my improved pump remains axiallybalanced despite changes in the pumping pressure or hydraulic pressure. r

The main pumping ports produce a radial It has already been proposed to counterbalance this radial thrust by appropriate radial balance ports'extending outside the gears in a direction parallel to the axes I of the linel-fl of Figs. 1 audit;

specification is accompanied bydrawings, in which:

Fig. 1 is an end elevation of a simple form of gear pump embodying features of my invention; s Fig. 2 is a longitudinal sectiontaken-in the plane of the line 2-2 of Figs. 1 and 3;

' 3 is an end elevation with the coverv plate removed, looking in the plane of theline 3-3 of Fig-2; I

Fig. 4 is a horizontal section taken in the plane Figs. 5 and 6 are diagrams explanatory of the invention; v n

Fig. '7 is an end elevation of another pump embodying features of my invention;

Fig. 8 is a section taken'in the planev of the line 8-4 of Fig. 7';

Fig. 9 is a schematic flow diagramiwith the pump piped in one manner; Y

Fig. 10-is a schematic flow diagram with the. pump piped in a different manner;

Fig. 11 is a sectionthrough the gear housing taken in the plane of the line ll-'-H of Fig. 12;

Fig. 12 is a section'through' the gear housing taken-in the plane of the' line I2--l'2'of Figs. 11- and 13; 1

Fig. 13 is a section through the gear housing taken in the plane of theline. I 3-" of Fig. 12;

with one Fig. 14 is a horizontal section through the pump body taken in the plane of the line i4-l4 of Fig. 7; r

Fig. 15 is a horizontal section through the pump body taken in the plane of the line l---l5 of Fig. 7;

Fig. 16 is an end elevation of the pump body;

Fig. 11 is a front elevation of the gear housing cover; 1 a-..

Fig. 18 is a vertical section therethrough taken in the plane of the line Iii-l8 of Fig. 17;

Fig. 19 is a section through the gear housing taken in the plane of the line Iii-I9 of Fig. 20;

Fig. 20 is a vertical section through the gear,

housing taken in the plane of the line 20--2D of Fig. 19;

Fig. 21 is a front elevation of a part of the pump body;

planatory of an advantage of a modification. Referring to the drawings, andmore particularly to Figs. 1 through 4, the gear pump there shown is a miniature pump intended for use as a lubricating oil pump for an internal combustion engine.

It comprises a driving gear I2 mounted on a a driving shaft l4, and meshing with a driven gear /municating, in the present case, with rearwardly extending passages 30 and 32. For some purposes these passages may be threaded for pipe connectionsj but this is not done in the present instance because the surface 34 of the pump is intended to be bolted against an appropriatmpart ofnthe engine, body. having openings registering with the passages 30 and 32. The holes 36 (Figs. 1 and 3) are provided to receive the bolts which hold. the pump against the engine body. The drive shaft l 4 is driven by a suitable pinion 38 meshing with a gear in the engine as, for example,.on the cam shaft, or other convenient part thereof.

The gears are helical gears for silence, but are so tiny that they are preferably single helical, rather than double helical or herringbone gears. The result is an opposite axial thrust which corresponds to the axial component of the gear tooth pre sure. Thus, referring to Fig. 5,- the driving gear 12 will be urged in one direction, as is indicated by the arrow 40, while the driven gear I6 will be urged in opposite direction, as is indicated by the arrow 42. The reason for this is diagrammatically shown in Fig. 6 which is supposedly taken in a plane extending transversely between the gears at their point of contact. The numeral 44 represents a driving tooth bearing against a driven tooth represented at 46. The reaction on the driving gezr tooth 44 is represented by vector 48, while the direct tooth pressure on the driven gear tooth 46 is represented by the opposite vector 50. Vector 48 has an axial component 52, and vector.50 has an axial component 54. These axial components produce an undesir The pumping ports are r invention is the provision of pressure ports in the casing at that face of the gear which tends to move toward the casing. In the present case, I shall assume the direction of rotation to be such 6 that pumping port 26 (Fig. 3) is a suction port and pumping port 28 a pressure port. Specifically, I provide axial balance pressure ports 56 and 58 (Fig. 1) on the outer face of driven gear 5, both ports being shown in Fig. 1, and one of the ports being shown in Fig. 4. The ports are formed by recesses in cover plate 22 and are preferably located diametrically opposite one another in order not to introduce any tilting force on the gear. The axial balance pressure ports for the driving gear I2 ar shown at 60 and 62 in Fig. 3, the latter port being also shown in Fig. 4. These ports are formed by recesses in the side wall 64 (Figs. 2 and 4) of the gear housing, and are preferably located diametrically opposite one another.

casing at that face of the gear which tends to move away from the casing. This is desirable for hydraulic reasons, and also so that the pump will be reversible. Thus, in the present case, I provide suction ports 66 and 68 (Fig. 1) in the cover plate .22 at the outer face of driving gear 12, these ports being shown in Fig. 1, and the port 66 being shown also in Fig. 4. I further provide suction ports 10 and I2 on the inner side of driven gear l6, these ports being shown in Fig. 3,

and the port 12 also being shown in Fig. 2.

It will be noted that the pressure ports 56 and 58 (Fig. 1) for driven gear is are located on the same side of the pump as the suction ports 66 and 68 for the driving gear l2, these ports all being in the cover plate 22, andthat the pressure ports 60 and 62 (Fig. 3) for the driving gear [2 are 10- cated on the same side of the pump as the suction ports 10 and 12 for the driven gear l6, these all being in the face wall 64 of the pump body. The axial balance ports thus create hydraulic thrusts opposite to the mechanical gear thrusts.

For any given pump pressure, the axial balance force-depends on the"e'ffective port area of the axial balance ports. When this area has been properly selected the pump will remain in balonce, even though operated at different pressures. This will be clear from the f ollowingior mula, in which: a

The diametrical pitch is DP The depth of the gear tooth is DP The helical gear thrust is Gr lbs.

The tangential gear load is Tr lbs. (the force required to drive the driven gear) The width of the gear tooth is W The helix angle is a The hydraulic pressure is p lbs. per square inch The mechanical efliciency of the pump is Em I prefer to also provide suction ports in the Gr=T.p tan a disregarding mechanical efliciency changes in pump pressure. v

I have so far discussed the matter of axial balance which is the primary purpose of the 76 present invention." However, the gears in a gear pump are also subject to radial thrust or unbal-.

tion port 80, and its effect on gear I6 is preferably compensated by a radial balance suction port 82. The effect of pump pressure port 28 on gear I2 is preferably counteracted by a radial balance pressure port 84, and its effect on gear I6 is counteracted by radial balance pressure port 86. The radial balance suction port 82 is clearly shown in Fig. 2 of the drawings.

In accordance with a feature and object of the present invention, the radial and axial balance ports are preferably combined in a convenient manner by simply locating the axial balance ports at the ends of the radial balance ports. Thus, an axial balance port may be considered a continuation of a radial balance port or vice versa, the complete port extending along the outside of the gear and turning around the a side face of the gear at one end or the other.

Specifically, axial balance pressure port 60 is formed at the inner end of radial balance pressure port 84. Axial balance pressure port 56 is formedat the outer end of radial balance pressure port 86. Axial balance suction port 12 is formed at the inner end of radial balance suction port 82. Axial balance suction port 66 is formed at the outer'end of radial balance suction port 80. The other axial balance ports are formed as direct continuations of the main pumping ports 26 and 28. Thus, axial balance pressure port 58 is formed at the outer end of pump pressure port 28, while axial balance pres sure port 62 is formed at the inner end of pump pressure port 28. Axial balance suction port 66 is formed at the outer end of pump suction port 26, andaxial balance suction port 10 is formed 'at'the inner end of pump suction port 26.

The balance ports should, of course, be connected to the pumping ports,'the balancepressure ports being connected to the pump pressure port, and the balance suction .ports being connected to the pump suction port. The necessary connections may be made by complex passages formed within the pumpcastings, but in the present case the desired connections are made in very simple fashion by'means of open channels formed in the-castings and effectively closed by only the side faces of the gears. Specifically, referring to Fig. 1,- the axial balance suction ports 68 and 68 are connected to one another and to the pump suction port by means of a diametrlcally extending passage 90.

This is formed on the inner face of cover plate 22, and is closed by-only the outer face wall of driving gear I2. Similarly; the radialbalance suction port 82 is connected'tothe pump suction port by means ofa passage 92 extending diametrically of the driven gear and closed solely by the outer face of the driven gear I6.

nected to one another and to the pump pressure port 28 by means of a diametrical passage 94, 96, the two parts being interrupted by the shaft I4. To connect the parts 94, 96, I employ an annular passage 98 extending around shaft I4.

It is more convenient to form this annular pas-.

sage in the gear I2, asis shown at 98 in Fig. 2, than to form it in the body of the pump, but either location may be used. The diametrical passage 94, 96 is, of course, an open channel formed in the face wall 64 of the pump body and closed solely by the inner face of driving gear I2.

The radial balance pressure port 86 is connected to the pump pressure port 28 by an open diametrical channel I00, I02 shown in Fig. 3.

These are connected by an annular passage I04 extending around the pin I8 of the driven gear. The annular passage I04 is preferably formed in driven gear I6, as is best shown in Fig. 2. The diametrical passage I00, I02 is an open channel which is closed by the inner face of driven gear I6.

It will be understood that while it is very convenient and inexpensive to employ communicating passages of the type here shown, they, however, affect the balance of the pump. Thus,

the suction passage 90 adds to the axial balance suction port area, while the suction passage 92 operates in negative sense, it being located at the pressure port side of the driven gear. 'Similarly, the pressure port passage 94, 96' adds to the axial balance pressure port area, while the passage I00, I02 acts in a negative sense, forit is located on the suction port side-of the pump. The resulting error is readily taken care of by appropriately modifying the size or area of the axial balance ports, the ports 66, 68,60, and 62 being reduced somewhat in area, or the ports 56,58, 10 and I2 being enlarged somewhatin area, or both.

As an illustration of the small size of the pump here under discussion, I may point out that'in one specific case the helical gears had a pitch diameter of 1.167 inches, an axial dimension of one inch, and were provided with fourteen teeth hav'- ing a helix angle of fifteen degrees and a pressure angle of twenty-eight degrees. The outside diameter of the gears was 1.333 and the root d-iaineter 0.990. Such a pump may be used to meet a minimum test performance of 1.25 gallons per minute at 650 revolutions per minute with an oil gauge pressure of twenty-five poundsp'er square inch, while using an oil such as Mobil A at degrees Fahrenheit. It will be understood that these dimensions are given solely by way of illustration and not in limitation of the invention.

Referring now to the remaining sheets of drawings, I there show a pump intended for use as a fuel pump for a household oil burner installation. 7

Referring first to Figs. 11, 12', and 13 the pump comprises a driving gear I20 meshing witha driven gear I22, these gears being housed in chambers formed in a flat plate-like gear housing I24. Plate I24 is enclosed between a pump body I26 and a gear housing cover I28. Gear housing I24 is provided with pumping ports I30 and I32 (Figs. 11 and 19) Itis also'provided with radial.

balance ports I34, I36, I38, and I40. All of 2 these ports pass entirely through the gear hous The pressure ports are connected-by 'diametrical passages at the opposite endof the pump. Specifically, and referring now to Fig. 3, the

axial balance pressure ports 60 and 82 are coning I24 (see Fig. 19) and their positions are re versed in Fig. 13 relativelto Fig. 11, because these show opposite sides of gear housing I24.

The radial balance ports I36 and I38 are connected to pumping port I 30 by channels or passages I42 and I44, as is shown in Figs. 11 and 12. The radial balance ports I34 and I40 are connected to pumping port I 32 by channels or passages I46 and I48, as is shown in Figs. 12, 13, and 19. The passages are located on opposite faces of the gear housing plate I24, and are closed when plate I24 is secured between the pump body I26 and the cover I28.

As before, the gears are single helical gears which produce opposite axial thrusts. These are counterbalancedby axial balance ports, and it is convenient, in the present case, to locate these in pairs which are diametrically opposite one another, and which are located at the ends of radial balance ports or pumping ports. In the present case, the axial balance ports are circular, being formed by drilling blind holes into the face walls enclosing the gear housing plate I 24. Altogether. there are eight such axial balance ports, two at each side ofeach gear. Four of these are visible in Figs. 11, 21, and 22, these being numbered I50, I52, I54, and I56. These are visible through the gear tooth spaces in Fig. 11, and are drilled into the pump body I26, as is indicated in Figs; 12 and 22. The ports I50 and I52 communicate with pumping port I30, the connection of port I50 being by way of the radial balance port I38, while the ports I54 and I56 communicate with the pumping port I 32.

The other four axial balance ports are indicated in Figs. 13 and 1'1, these being marked I58, I80, I62, and IE4. In Fig. 13 these ports are seen through the gear tooth spaces. They are drilled into the cover plate I28, as is indicated in Figs. 12 and 18. The ports I58 and I60 communicate withthe pumping port I32, while the ports I62 and I64 communicate with the pumping port I30, the connectionof port I64 being by way of the radial balance port I38.

The relation of the gear housing to the comtail, the pump body I26 is provided with inlet Y passages I82 and I84 near the upper corners thereof. These communicate with holes I86 extending in the direction of the axis of the pump and leading to points outside the strainer I12, as is clearly shown in Fig. '7. It will be understood that the strainer is soldered or otherwise sealed to the turned edge I 88 (Fig. 8) of a plate or strainer flange I80, the latter being locked between the strainer cover I14 and the pump body I26. Suitable gaskets may be used at each side of the strainer flange I80 to insure a fluid tight connection. The strainer I12 may, if desired, be supported against bending or collapse by a suitable frame or support I94. The incoming liquid flows into the space between strainer cover I14 and strainer I12, and then flows inwardly through strainer I12 to the gear housing.

The liquid then flows through gear housing cover I28 to the suction port of the pump. There are two openings for this purpose, marked I86 and I98 in Fig. 7, the latter being closed by a plug and the former acting as an inlet. Referring to Figs. 7, 11, and 17, it should be understood that the inlet hole I96 leads directly to the pumping port I30, and that the hole I88 leads to the pumping port I32. In the present case, with hole I88 blocked, the pumping port I30 acts as a suction port, while pumping port I32 acts as a pressure port.

The liquid discharged by the gears -flows in opposite direction, that is, toward the right'or into the pump body I26, as viewed in Fig. 8.

Specifically, the pump body is provided with holes 200 and 202 (Fig. '1) extending axially of the pump until they run into vertical holes 204 plete pump is best shown in Figs. '1 and 8,

The entire gear housing isenclosed within a.

large area strainer I12, which in-turn is housed within a strainer cover I14, the latter being shown in- Fig. 8 but omitted in Fig. 7. The cover I14 is secured to the pump body I26 by suitable fastenings, in this case, six crews I16, the threaded holes for receiving which are shown in the pump body at I18 in Fig. '1.

All piping is, for convenience, connected to the pump body. This includes an inlet pipe, a discharge pipe, and a by-pass pipe 'for return of excess fuel .oil to the storage tank. The p body is made with symmetrical passages, so that the piping may be connected in either direction,

the unused passages being blocked'by suitable plugs. For this reason, there are six pipe connections instead of three. Moreover, some of the internal passages within the pump may be reversed to accommodate rotation of the pump described in detail here, except for brief mention of flow connections to the same.

Considering the arrangement in greater de- 202 leading to vertical passages 204 and 206 are clearly shown in Fig. 14, looking downward, while the lower ends of passages 204 and 206 leading into the by-pass chamber I80 are clearly shown and 202 to be located at downwardly offset I points.

As before, only one or the other of these communicatlngpassages is used at any one time. It is convenient to plug the passage at a point I near the by-pass chamber I80. In the present V connections 2 and 2I6 (Figs. '1 and ,8). passages open directly into the bypass cham-' case, the vertical passage 204 is plugged at 2I2, as is shown in Figs. '1, 8, and 15. Thus, the passages 202 and 206 are effective, the passage 202 communicating with the pumping port I32, which is as it shouldbe, v

The pump body I26 is provided with two pipe These Fig. 9. Liquid is piped into the pump body at I82 and thenflows forwardly through hole I88 to the region surrounding the strainer I12. The liquid then flows through the strainer and rearwardly through hole I96 to pumping port I30.-

The liquid is pumpedsaround with the gears to pumping port I32, and then flows rearwardly through hole 202, and then downwardly at 206 to a. suitable by-pass unit 220 in the by-pass chamber I80. The discharge pipe is connected to the end 222 of by-pass unit' 228, the opposite 7 end being a closed end. By-pass fluid flows downwardly through passage 2. A pressure gauge 224 may be connected at passage 2I6, or passage 2| 6 may be simply blocked by a plug.

, If it is more convenient to connect thepiping in opposite fashion, then the arrangement will operate as shown in Fig. 10, there being an inlet pipe connected at I84 leading through forward passage I88 to the region surrounding strainer II2, whereupon the liquid flows through the strainer to passage I98 leading to pumping port I32. The liquid then moves around with the gears to pumping port I30, and then flows rearwardly through passage 200 and then downwardly through passage 204 to by-pass unit 228,

inserted in by-pass chamber I80 in reversed popump. This is not at all the case. Once the inlet liquid surrounds the strainer, it 'is accespressure, the shaft tends to move to the right and there is no thrust on the screw. In all normal cases the delivery pressure exceeds thesuction, and the force tending to move the shaft to the right exceeds the forcetending to move the shaft to the left. The movement to the right is limited byshoulder 23I of end cover 233. It is desirable to eliminate any effect of these elements on the axialbalance of the driving gear I20. Accordingly, in the present pump the shaft 230 isslidably keyed to the driving gear I20. Referring to Figs. 11 and 13, the driving shaft 230 is provided with a transverse pin or key 240,

the ends of which are received in splines or keyways formed on the inside of driving gear I20.

The driven gear I22 is freely rotatable and f-reely axially slidable on a pin or stationary shaft 242, the latter being're'ceived with a force fit in the pump body I28.

Referring to Fig. 8 the pump body may be bolted to the rest of the machine by a suitable flange located at the point 2. The projections 248 of this flange are best shown in Figs. 14 and 16, these being provided with holes 248 for suitable mounting bolts. Figs. 14 and 16 show the pump body alone, the shaft and the parts of the sealbeingremoved'.

Y In a'speciflc case, some of the leading dimen- 1 sions of the pump follows: 1

-The gears have an outsidediameter of 0.703

heretofore described were as inch, a root diameter of 0.5292 inch, and a pitch sible to either p'umping port. The location of' the dischargepassage and the by-pass unit is related to the direction of rotation, but in Fig.

hand comer, and in Fig. 10, the inlet pipe may be connected at the upper left-hand corner, instead of the upper right-hand comer, accord- 9 the inlet pipe may be connected at the upper right-hand corner, instead of the upper lefting to greatest convenience in-mak'ing the necessary pipe connections. To express the matter in a different manner, the direction of rotation determines the character of the pumping ports,

which in turn determines the location-of the x plugs located within the pump-specifically, the

plugs I98 and 212 in'the present case. The pipe diameter of 0.625 inch, a face width or axial dimensionof 0.3084 inch. The gears have fifteen 'teeth with a helix angle of twenty-three degrees,

and a pressure angle of twenty-eight degrees. The dianietral pitch in the plane of rotation is twenty-four. This pump has a capacity of twenty-two gallons per hour without the by-pass acthan at 1750 R. P. M. and zero pressure.-

It will be understood that these dimensions are given solely by wayof illustration and not in limitation of the invention. They show the small size of the gears used, thus indicating the dim- V 'culty or impracticability of providing double neli cal gears in such small dimensions, 3

Before concluding the description, itmay be pointed out that once the balance ports and end connections determine the location of the external plugs.

Referring now to Fig. 8, the driving gear I28 is driven by a driving shaft 230, the latter passing through the pump body and being sealed by an appropriate seal, the diaphragm of which is numbered 232. The seal may be of the conventional mechanical surface sealing type and need not be described in detail. This seal includes a spring 234. The inner side of the sealing membrane is exposed to the suction side of the pump through a' passage 236. This leads toa hollow space 231, which in tum-is connected to the pumpingports by horizontal passages 288 and be shown with reference to 23 of the draw- A Thus 2 (Figs. 7 and 21), one bf which, that leading to the pressure port, is blocked off by screw 243.

The passages 238 and 2 lead to the upwardly extending partsofthe enlargements 208 and 2I0 (Figs. 13 and 19).

These things lead to an axial thrust on the shaft which. when thepump is not operating under pressure, may be counteracted by-an end thrust bearing or screw 238. it is under plates have been worked out for a pump using gears of a certain diameter, the capacity orthe pump may be changed by changing the axial dimension-or width of the gears without changing diameter. In suchcase, redesign of the port a may be avoided by appropriately changing the helix angle of the gears. This may ings, in which gears of. different width, W and W1, are assumed to have a diflerent helix angle A and A1, such as to produce the samedead L.

L tan M QReverlihg to the formula given earlier in the specification: 7

W .1 I G tan tip- This may be rewritten as: A v 1 E i-i=1. .2.

Now for a modified gear having a-"greater axial width, but a smaller helix angle, we may write which is the same as before. Thus the thrustto be balanced is independent of the gear width,

and is the same when the lead is the same.

It is not essential to use diametrically opposite axial balance ports. In some cases it may be preferred to use a single axial balance port and in such case it would preferably be the port near the contact point of the gears, that is, at the end of the pumping port. This arrangement may be used to help reduce a tilting force on the gear caused by the axial component of the gear tooth pressure. the axial component of the gear tooth pressure is represented by arrow 250, this would ordinarily be counteracted at the shaft as is indicated by arrow 252, thus providing a tilting moment, the lever arm of which is indicated at 254. If, howthe ports I52 and I54, these, however, being appropriately increased in area.

It is believed that the construction, operation, and principles underlying my new pump, as well as the many advantages of the same, will be apparent from the foregoing detailed description thereof. The advantage of silent operation is obtainedwhile using single helical gears. This lowers the cost of the pump and makes it possible to employ helical gears in relatively tiny pumps despite their small size. However, the invention is not limited to very small pumps. For example, in gasoline dispensing pumps, it has been proposed to eliminate all noise due to the mating of metallic gears by using one gear made of metal, while the other is made of a plastic. Double helical pump gears are usually standardized at a helix angle of approximately thirty degrees. The plastic material tends to chip at the sharp corners of the teeth. With a single helical gear, various other helix angles may be used, for example, fifteen degrees or'eighteen degrees. This avoids chipping of the plastic material. The invention is, therefore, of value for freedom in the selection of helix angle, as well as for economy, because single helical gears are much cheaper than double helical gears. They are also available in a greater range of sizes and angles. Also, the molding of double helical gears presents considerable practical difficulties, compared to the molding of single helical gears.

It will be apparent that while I have shown and described my invention in several preferred forms, many changes and modifications may be made in the structures disclosed without departing from the spirit of the invention defined in the following claims.

I claim:

1. A gear pump comprising a driving gear, a

" driven gear, a casing surrounding said gears and providing suction and pressure pumping ports leading to said gears, said gears having side faces and being single helical gears resulting in axial Thus, referring to Figs. 24 and 25, if p thrust, and means to counterbalance said axial thrust, said means including an axial balance port of limited area in the casing opening into that face of the gear whichtends to move toward the casing, the axial'balance port for one of the gears being on the opposite side of the casing from the axial balance port for the other gear, said ports being located near the peripheries of the gears, and non-restrictive passages freely connecting the pump pressure port to the axial balance ports,

2. A gear pump comprising a. driving gear, a driven gear, a casing surrounding said gears and providing suction and pressure pumping ports leading to said gears, said gears being single helical gears resulting in axial thrust, and means to counterbalance said axial thrust, said means including an axial .balance pressure port in the casing at that face of the gear which tends to move toward the casing, an axial balance suction port in the casing at that face of the gear which tends to move away from the casing, the axial balance pressure port for one of the gears being on the same side of the casing asthe axial balance suction port for the other gear, non-restric-' tive passages freely connecting the pump pressure port to the axial balance pressure ports, and non-restrictive passages freely connecting the pump suction port to the axial balance suction ports.

3. A pump as defined in claim 2, in which the connecting passages are open channels formed in the end wall of the casing and extending diametrically of the gears, whereby the adjacent faces of the gears function to close the open side of the channels, there being an annular groove around the shafts of the gears where the aforesaid dia'metrical passages are interrupted by a shaft.

4. A pump as defined in claim 2, in which the driving gear is splined to the driving shaft so that the gear is independent of axial movement of the shaft.

.5. A gear pump comprising a drivin gear, a driven gear, a casing surrounding said gears and providing suction and pressure pumping ports leading to said gears, said gears having side faces and being single helical gears resulting in axial thrust, and means to counterbalance said axial thrust, said means including a plurality of axial balance ports of limited area in the casing opening onto that face of the gear which tends to move toward the casing, the axial balance ports for one of the gears being on the opposite side of the casing from the axial balance ports for the other gear, said ports being located near the peripheries of the gears, and non-restrictive pas-.

sages freely connecting the pump pressure port to the axial balance pressure ports.

6. A gear pump comprising a driving gear, a driven gear, a casing surrounding said gears and providing suction and pressure pumping ports leading to said gears, said gears being single helical gears resulting'in axial thrust, and means to counterbalance said axial thrust, said means including a plurality of axial balance pressure ports in the casing at that face of the gear which tends to move toward the casing, and a plurality of axial balance suction ports in the casing at that face of the gear which tends to move away from the casing, the axial balance pressure ports for one of the gears being on the same side of the that the gear is in of the shaft.

. v 2,888,085 necting the'pump pressure port to the axial balance pressure ports, and non-restrictive passages freely connecting the pump. suction port to the axial balance suction ports. 7

'7. A gear pump comprising a driving gear, a driven gear, a casing surrounding said gears and providing suction and pressure pumping ports leading to said .gear's, said gears having side the gear so as not to produce any tilting moment on the gear, the axial balance ports. for one of the gears being .on the opposite side of the casing from the axial balance ports for the other gear,

and non-restrictive passages freely connecting the pump-pressure port to the axial balance ports. 8. A gearpump comprising a driving gear, a

that face of the gear which tends to move .away

from the casing, the axial balance ports for each 35 gear being symmetrically located with respect to the gear so as not to produce any tilting moment on the gear, the axial balance pressure ports for 1 one of the gears being on the same side of the casing as the axial balance suction ports for the other gear, non-restrictive passages freely con- .necting the pump pressure port to the axialbalgice pressure ports, and non-restrictive passages freely connecting the pump suction port to the axial balance suction ports.

9. A pump as defined in claim 8, in which the connecting passages are open channels formed in the end wall of the casing and extending diametrically of the gears, whereby the adjacent faces ofthe gears function to close the open side of the channels, there being an annulargroove around the shafts of the gears where the aforesiiacitdiametrical passages are interrupted by a s l 10. A pump as defined in claim 8, in whichthe driving gear is splined to the driving shaft so dependent of axial movement 11. A gear pump comprising driving and driven gears, a casing surrounding said gears and including suction and pressure pumping ports leading to said gears, said ports producing a radial thrust on said gears, said gears having side faces and being single helical gears which develop an axial thrust, hydraulic balance'means for ooun teracting the radial thrust, said means including radial balance ports extending in the direction of axial gear thrust, said means including" axial balance ports of limited area in the casing opening onto that face of the gear which tends to movetoward the casing, the axial balance ports of one gear being .on the opposite side of the casing from the axial balance ports of the other gear, said ports beinglocated near the peripheries of the gears, and appropriate non-restrictive 6 passages for freely connecting the balance ports to the pump pressure port.

12. A gear pump comprising driving and driven gears, a casing surrounding said gears and including suction and pressure pumping ports leading 10 to said gears, said ports producing a radial thrust on said gears, said gears being single helical gears which develop an axial thrust, hydraulic balance means for counteracting the radial thrust, said means including radial balance pressure ports extending in the direction of the axes'of the gears at points diametrically opposite the pump pressure port, and radial balance suction ports extending in the direction of the axes of the gears at points diametricallyiopposite the pump suction 0 port, hydraulic means for hydraulically counterbalancing the axial gear thrust, said means 'in-' cluding'axial balance pressureports in the casing at that face of the gear which tends to move toward the casing, and axial balance suction ports in the casing at that face of the gear which tends to move away from the casing, the axial balance pressure ports of one gear being on the same side of the casing as the axial balance suction ports of the other gear, and appropriate non-restrictive passages for freely connecting the balance pressure ports to the pump pressure port, and for freely connecting the balance suctionports to the pump suction port.

' 13. A gear pump comprising driving and driven gears, a casing surrounding said gears and iningto said gears, the fluid in'said-ports producing a radial thrust on said gears, said gears being single helical gears which develop an axial thrust,

hydraulic balance means for counteractingthe.

and the pump pressure port, and appropriate passages for connecting the bal pump pressure port.

14. A gear pump comprisin gears, a casing surrounding said gears and including suction,- and pressure pumping ports leading to said gears, the fluid in s'aid'ports producing a radial thrust on said gears, said gears being single helical gears which develop-an axial thrust, hydraulic.balance means for counteracting theradial thrust, said means including radial 05 balance pressure ports extending in the direction of the axes ofthe gears at points diametance ports to the rically opposite the pump pressure port, andrfi'adial balance suction ports extending in the; di-' rection of the axes of the gears at points diametrically opposite the pump, suction port, hy-

draulic means for hydraulicallycounterbalancing the axial gear thrust, said means including axial balance pressure ports in the casing at that face ing, and axial balance suction ports in the cascluding' suction and pressure pumping ports leadg driving-and driven of the gear which tends to move toward the cas-' ing at that face of the gear which tends to move away from the casing, the axial balance pressure ports of one gear being on the same side of the casing as the axial balance suction ports of the other'gear, the axial balance pressure ports beingformed directly at the ends of the radial balance pressure ports and the pump pressure port, the axial balance suctionports being formed directly at the ends of the radial balance suction ports and the pump suctionport, and appropriate passages for connecting the balance pressure ports to the pump pressure port, and for connecting the balance suction ports to the pump suction port.

15. A pump as defined in claim 14, in which the connecting passages are open channels formed in the end wall of the casing and extending diametrically of the gears, whereby the adjacent faces of the gears function to close the open side of the channels, the pressure channels being in one end wall and the suction channels being in the opposite end wall of the casing, there being an annular groove around the shafts of the gears where the aforesaid diametrical passages are interrupted by a shaft.

16. A gear pump comprising a driving gear, a driven gear, a casing surrounding said gears and providing suction and pressure pumping ports leading to said gears, said gears being single, helical gears resulting in axial thrust, and means to counterbalance said axial thrust, said means including an axial balance pressure port in the casing at that face of each gear which tends to move toward thecasing, an axial balance suction port in the casing at that face of each gear which tends to move away from the casing, whereby .each gear is subjected to both pressure and suction forces operating in the same direction, the axial balance pressure port for one of the gears being on the same side of thecasing as the axial balance suction port for the other gear, passages freely connecting the pump pressure port to the axial balance pressure ports, and passages freely connecting the pump suction port to the axial balance suction ports, the pump balance being maintained substantially independently of the pressure and suction heads at which the pump is operated, and the suction and pressure ports being so interchangeably arranged in the casing that the pump is reversible.

17. A gear pump comprising a driving gear, a driven gear, a casing surrounding said gears and providing suction and pressure pumping ports leading to said gears, said gears being single helical gears resulting in axial thrust, and means to counterbalance said axial thrust, said means including two axial balance ports of circumferentially limited area in the casing near the periphcries of the gears and opening onto that face of each gear which tends to move toward the casing, the two axial balance ports for each gear being recessed into the casing wall and being diametrically opposite one another, with a first one of said balance ports being located at and communicating directly with the pressure pumping port, and the second of said balance ports communicating with the first, the two axial balance ports for one of the gears being on the opposite side of the casing from the two axial balance ports for the other gear, and passages freely connecting the pump pressure port to the axial balance pressure ports.

18. A gear pump comprising a driving gear, a driven gear, a casing surrounding said gears and providing suction and pressure pumping ports leading to said gears, said gears being single helical gears resulting in axial thrust, and means to counterbalance said axial thrust, said means including two axial balance pressure ports in the casing at that face of each gear which tends to move toward the casing, and two axial balance suctionports in the casing at that face of each gear which tends to move away from the casing, whereby each gear is subjected to both pressure and suction forces operating in the same direction, the two axial balance ports on each side of each gear being diametrically opposite one another, the axial balance pressure ports for one of the gears beingon the same side of the casing as the axial balance suction ports for the other gear, passages freely connecting the pump pressure port to the axial balance pressure ports, and passages freely connecting the pump suction port to the axial balance suction ports, the pump balance being maintained substantially independently of the pressure and suction heads at which the pump is operated, and the suction and pressure ports being so interchangeably arranged in the casing that the pump is reversible.

19. A gear pump comprising driving and driven gears, a casing surrounding said gears and including suction and pressure pumping ports leading to said gears, the fluid in said ports producing a radial thrust on said gears, said gears being single helical gears which develop an axial thrust, hydraulic balance means for counteracting the radial thrust, said means including radial balance ports extending generally'ln the direction of the axes of the gears atpoints diametrically opposite the pressure pumping port, and hydraulic balance means for hydraulically counterbalancing the axial gear thrust, said means including ,two axial balance ports of circumferentially limited area in the casing opening onto that face of each gear which tends to move toward the casing, the axial balance ports of one gear being on the opposite side of the casing from the axial balance ports of the other gear, said axial balance ports being located so near the peripheriesof the gears that they open onto the. tooth ends of the gears, the two axial balance ports on one side of a ear being diametrically opposite on another, with 1 one of them located at and communicating diing a radial thrust on said gears, said gears being single helical gears which develop an axial thrust, hydraulic balance means for counteracting the radial thrust, said means including radial balance pressure ports extendin generally in the direction of the axes of the gears at points diametrically opposite the pump pressure port, and radial balance suction ports extending generally in the direction of the axes of the gears at points diametrically opposite the pump suction port, hydraulic means for hydraulically counterbalancing the axial gear thrust, said means including two axial balance pressure ports in the casing at that face of each gear which tends to movetoward the casing, and two axial balance suction ports in the casing at that face of each gear which tends to move away from the casing, whereby each gear is subjected to both pressure and suction forces diametrically opposite one another, with one of 1 said two axial balance ports located at and communicating directly with a, pumping port, and the other of said two axial balance port being located at and communicating directly with one 2,888,065 I 9 end of a radial balance port. the axial balance pressure ports or one gear being on the same side of the casing as the axial balance suction ports of the other gear, and appropriate passages for freely connecting the balance pressure ports to one another and the pump pressure port, and

for ireely connecting the balance suction ports to one another and the pump suction port.

GUSTAVE A. UNGAR. 

